According to the developers of ARK: Survival Evolved, the game has the capability of pairing PS4 and Xbox One players together, but it won't happen because Sony is saying no.
In yet another case in Sony's refusal to allow cross-platform play, ARK: Survival Evolved co-creative director Jeremy Stieglitz told his Twitter followers that the studio has cross-play working internally.
Stieglitz was asked if it'll ever be a realty, however, and his answer wasn't very encouraging.
We have it working internally, but currently Sony won't allow it :(
— Jeremy Stieglitz (@arkjeremy) August 18, 2017
This sounds eerily similar to what Rocket League developer Psyonix said when asked the same question a while ago. Rocket League supports cross-play between all platforms, except PS4.
This is also the case for Minecraft, which supports the same feature on all platforms except PS4. It's not clear why Sony insists on blocking cross-platform play for most developers, while making it available selectively for others like in the case of Street Fighter 4, and Final Fantasy 14.
ARK: Survival Evolved is out August 29 on PC, PS4, and Xbox One. The game is currently in Early Access.